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← JEE Main 2016 · 10 Apr · Shift 1
MathematicsSingle correct+4 / -1Question 68 of 90

JEE Main 2016 · 10 Apr · Shift 1, Mathematics question 68

Let a1,a2,a3,…,an,…a_1, a_2, a_3, \dots, a_n, \dots be in A.P. If a3+a7+a11+a15=72a_3+a_7+a_{11}+a_{15}=72, then the sum of its first 17 terms is equal to :

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Answer and worked solution

Official answer: A

a3+a15=a7+a11=2a9a_3+a_{15}=a_7+a_{11}=2a_9, so a9=18a_9=18 and S17=17a9=306S_{17}=17a_9=306.

Topics:Arithmetic progression
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